Fabrication of finely featured devices by liquid embossing

ABSTRACT

Elastomeric stamps facilitate direct patterning of electrical, biological, chemical, and mechanical materials. A thin film of material is deposited on a substrate. The deposited material, either originally present as a liquid or subsequently liquefied, is patterned by embossing at low pressure using an elastomeric stamp having a raised pattern. The patterned liquid is then cured to form a functional layer. The deposition, embossing, and curing steps may be repeated numerous times with the same or different liquids, and in two or three dimensions. The various deposited layers may, for example, have varying electrical characteristics, interacting so as to produce an integrated electronic component.

PRIOR APPLICATION

[0001] This application stems from U.S. Provisional Application SerialNo. 60/153,776, filed on Sep. 14, 1999, and No. 60/167,847, filed onNov. 29, 1999.

FIELD OF THE INVENTION

[0002] The present invention relates to fabrication of finely featuredelectronic, chemical, and mechanical devices.

BACKGROUND OF THE INVENTION

[0003] Electronic and electromechanical components are presentlyfabricated in large, immobile manufacturing facilities that aretremendously expensive to build and operate. For example, semiconductordevice fabrication generally requires specialized microlithography andchemical etching equipment, as well as extensive measures to avoidprocess contamination. The total amount of time required for processingof a single chip may be measured in days, and typically requiresrepeated transfer of the chip into and out of vacuum conditions.

[0004] In addition to their expense, the fabrication processesordinarily employed to create electronic and electromechanicalcomponents involve harsh conditions such as high temperatures and/orcaustic chemicals, limiting the ability to integrate their manufacturewith that of functionally related but environmentally sensitiveelements. For example, the high temperatures used in silicon processingmay prevent three-dimensional fabrication and large-area fabrication;these temperatures are also incompatible with heat-sensitive materialssuch as organic and biological molecules. High temperatures alsopreclude fabrication on substrates such as conventional flexibleplastics, which offer widespread availability and low cost.

[0005] Despite intensive effort to develop alternatives to theseprocesses, no truly feasible techniques have yet emerged. U.S. Pat. No.5,817,550, for example, describes a low-temperature roll-to-roll processfor creating thin-film transistors on plastic substrates. This approachfaces numerous technical hurdles, and does not substantially reduce thelarge cost and complexity associated with conventional photolithographyand etching processes.

[0006] U.S. Pat. No. 5,772,905 describes a process called “nanoimprintlithography” that utilizes a silicon mold, which is pressed under highpressure and temperature into a thin film of material. Following coolingwith the mold in place, the material accurately retains the features ofthe mold. The thin film may then be treated to remove the small amountof material remaining in the embossed areas. Thus patterned, the filmmay be used as a mask for selectively etching underlying layers offunctional materials. This process is capable of producing patterns withvery fine resolutions at costs significantly below those associated withconventional processes. But it is quite complicated, requiring numeroustime-consuming steps to create a single layer of patterned functionalmaterial. The technique requires high application pressures andtemperatures at very low ambient pressures, thereby imposing significantcomplexity with attendant restriction on the types of materials that canbe patterned. Perhaps most importantly, this technique is limited toproducing single-layer features, thereby significantly limiting itsapplicability to device fabrication.

[0007] U.S. Pat. No. 5,900,160 describes the use of an elastomeric stampto mold functional materials. In particular, the stamp is deformed so asto print a self-assembled molecular monolayer on a surface. Thisprocess, also called MIMIC (Micromolding Against Elastomeric Masters),is significantly simpler than nanoimprint lithography, and can beperformed at ambient temperatures and pressures. But the technique isgenerally limited to low-resolution features (in excess of 10 μm), andmore importantly, the types of geometries amenable to molding by thistechnique are limited.

DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION

[0008] It is, accordingly, an object of the present invention to providean easily practiced, low-cost process for directly patterning functionalmaterials without the need for multistage etching procedures.

[0009] Another object of the invention is to increase the speed withwhich layers of functional materials can be patterned.

[0010] Still another object of the invention is to provide a fabricationprocess that requires no unusual temperature, pressure, or ambientconditions, thereby increasing the range of materials amenable topatterning.

[0011] A further object of the invention is to facilitate convenientnanoscale patterning of multiple adjacent layers.

[0012] Yet another object of the invention is to planarize depositedmaterials as part of the application process, eliminating the need foradditional planarizing processes (such as chemical mechanicalpolishing), thereby facilitating fabrication of complexthree-dimensional devices employing many (e.g., in excess of 100)layers.

BRIEF SUMMARY OF THE INVENTION

[0013] To achieve the foregoing and other objects, the present inventionutilizes an elastomeric stamp to facilitate direct patterning ofelectrical, biological, chemical, and mechanical materials. Inaccordance with the invention, a thin film of material is deposited on asubstrate. The deposited material, either originally present as a liquidor subsequently liquefied, is patterned by embossing at low pressureusing an elastomeric stamp having a raised pattern. The patterned liquidis then cured to form a functional layer. The deposition, embossing, andcuring steps may be repeated numerous times with the same or differentliquids, and in two or three dimensions. The various deposited layersmay, for example, have varying electrical characteristics, interactingso as to produce an integrated electronic component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The foregoing discussion will be understood more readily from thefollowing detailed description of the invention, when taken inconjunction with the accompanying drawings, in which:

[0015] FIGS. 1A-1D are greatly enlarged sectional views illustratingfabrication of an elastomeric stamp in accordance with the presentinvention;

[0016]FIGS. 2A and 2B are side elevations illustrating application of athin, uniform film of liquid onto a substrate;

[0017] FIGS. 3A-3C and 3D-3F are sectional views illustrating,respectively, the embossing process of the present invention as appliedto planar surfaces and non-planar surfaces;

[0018] FIGS. 3G-3I are sectional views illustrating planarization andthe creation of vias using the present invention;

[0019] FIGS. 4A-4F are sectional views illustrating fabrication of anelectronic inverter in accordance with the present invention;

[0020] FIGS. 5A-5F are plan views of the structures shown sectionally inFIGS. 4A-4F;

[0021] FIGS. 6A-6G are sectional views illustrating fabrication of amicroelectromechanical device in accordance with the present invention;

[0022] FIGS. 7A-7G are plan views of the structures shown sectionally inFIGS. 6A-6G;

[0023] FIGS. 8A-8F are sectional views illustrating fabrication of abiochip in accordance with the present invention;

[0024] FIGS. 9A-9C schematically illustrate, respectively, a single SRAMcircuit, a two-dimensional array of such circuits, and athree-dimensional array of such circuits;

[0025]FIGS. 10A and 10B are sectional views illustrating fabrication ofa field-emission display device in accordance with the presentinvention;

[0026]FIG. 11 is a block diagram of a preferred nano-embossing systemimplementing the present invention; and

[0027]FIGS. 12A and 12B schematically illustrate alternativeconfigurations for synthesizing nanoparticles.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] FIGS. 1A-1D illustrate an exemplary approach to fabricating anelastomeric stamp useful in the practice of the present invention. Asshown in FIG. 1A, a substrate 100 is patterned with a series of recessedfeatures 105 and projecting features 110. These features correspond insize and arrangement (but not in depth) to the pattern ultimatelydesired for a component layer. Accordingly, the features 105, 110 may beinscribed using conventional techniques such as photolithography,e-beam, focused ion-beam, micromachining, or other lithographicapproaches. Feature sizes as small as 150 nm have been accuratelyobtained and utilized, although even smaller features are of coursepossible. Substrate 100 may, for example, be any surface of sufficientsmoothness that may be conveniently patterned, and which will not bondto the material from which the stamp is to be formed. Suitable materialsinclude, for example, silicon, metal wafers, and exposed photoresist.

[0029] As shown in FIG. 1B, a raised enclosure 115 is applied tosubstrate 100 so as to surround the pattern of features 105, 110.Enclosure 115 may be, for example, a metal or plastic wall, the outercontour of which is designed to fit within the device that will applythe stamp as hereinbelow described. An uncured elastomer 120 in liquidform is poured into the well 125 formed by enclosure 115 and features105, 110. Preferably, elastomer 120 is a curable rubber or siliconematerial such as polydimethylsiloxane (PDMS), e.g., the SYLGARD-184material supplied by Dow Corning Co. To prevent seepage, enclosure 115is desirably held against the surface of substrate 100 with a modestpressure or set within a conforming groove in substrate 100.

[0030] A sufficient amount of elastomer 120 is poured into well 125 tocompletely fill features 105 and to provide a stable body mass forstamping operations. The elastomer 120 is then cured into a solid plug130. For example, the PDMS material mentioned above may be cured byheating in an oven at 80° C. for 2 h. Other silicone elastomers may becured by exposure to moisture, e-beam or actinic (e.g., ultraviolet)radiation, or by addition of a cross-linking agent.

[0031] The solid plug 130 is separated, with or without enclosure 115,from substrate 100 as shown in FIG. 1D to form a finished stamp 132. Theunderside of plug 130 has a series of projecting and recessed features135, 140 complementary to the features 105, 110 of substrate 100, whichare left undamaged by the foregoing process steps; moreover, little ifany elastomer is desirably left on the substrate 100 when plug 130 isremoved.

[0032] Enclosure 115 may be removed along with plug 130 as shown in FIG.1D, or it may instead be left in place on substrate 100. If it isremoved and its association with plug 130 retained, it may serve severalpurposes: facilitating mechanical attachment to the stamping device,assisting with alignment of the stamp (for example, enclosure 115 mayhave an alignment tab that mates with a complementary recess in thestamping device), and limiting lateral deformation of plug 130. Tofurther limit lateral deformation, plug 130 may be made relatively thin(by pouring the liquid elastomer 120 to a level not substantially abovethe surface of substrate 100) and capped by a solid support structure. Afenestrated film or other rigidity-conferring filler material may beadded to liquid elastomer 120 prior to curing, thereby integratingwithin the resulting polymer matrix to further enhance the rigidity ofplug 130.

[0033] Other techniques may also be used to fabricate the stamp 132. Forexample, a stamp may be patterned by selectively curing a thin film ofthe elastomer by exposure to actinic radiation through a mask followedby photochemical development (to remove the exposed or the unexposedareas), or by selective thermal curing with an atomic force microscope(AFM) thermal tip. The stamp 132 may also be fabricated fromnon-elastomeric stiff materials for better control of deformation. Forexample, the procedures described above can be carried out with apolyacrylate rather than an elastomer. Suitable polyacrylates includepolyfunctional acrylates or mixtures of monofunctional andpolyfunctional acrylate that may be cured by e-beam or ultraviolet (UV)radiation.

[0034] If the stamp 132 becomes soiled, it may be cleaned by coating thepatterned surface with a liquid polyimide such as Japanese SyntheticRubber, curing the polyimide in place, and then peeling it off thestamp. This process will remove dust and debris without harming thepatterned stamp surface.

[0035] The stamp is applied to a liquid which, when cured, provides adesired electrical, chemical, biological, and/or mechanicalfunctionality. For example, the liquid may be a colloidal dispersion ofnanoparticles or carbon nanotubes; an uncured polyimide; a solution ofbiological material; or a solution of a suitable sacrificial or releaselayer which may later be dry- or wet-etched (e.g., PMMA). In general,the liquid is present on a substrate (or on a previously deposited andcured layer) as a thin, uniform film. A deposited liquid can be drawninto such a film by various techniques, one of which is illustrated inFIGS. 2A and 2B. A substrate 200—which may be a glass slide, a siliconwafer, a sheet of plastic, or other smooth material—receives a bead 210of liquid. A smooth rod 220 (which may be glass or a flexible material)is dragged across substrate 200 in the direction of the arrow, drawingthe bead 210 into a uniform film 230. In general, the pressure betweenrod 220 and substrate 200 can vary without affecting the resultantthickness of film 230; indeed, rod 220 can even be held slightly abovesubstrate 200 (so that no contact is actually made). The speed withwhich rod 220 is drawn across substrate 200 does affect the thickness offilm 230, however, with faster travel resulting in a thinner film.Accordingly, for a film of uniform thickness, rod 220 should be drawn ata constant speed, and should not be allowed to rotate as it is drawn.The film thickness is also affected by the size (diameter) of rod 220.

[0036] After rod 220 has been fully drawn across substrate 200, the film230 will typically still be in a liquid state. Depending on the liquid,substantial loss of volume may occur by evaporation; indeed, a loss of90% of the initial height of the film is not unusual. Thus, a thin filmof liquid initially 100±10 nm in height may dry down to a film 10±1 nmin height. We have routinely obtained dry films with heights less than40 nm using this technique.

[0037] For some materials, the use of a rod to produce a thin film isnot an option. For example, the material may not wet to the surface ofsubstrate 200, or the solvent may evaporate almost instantly. Analternative application technique useful in such cases utilizes a stamphaving a patterned surface as described above. A small line of theliquid material to be drawn into a film is deposited onto substrate 200.One edge of the stamp is brought into contact with substrate 200immediately next to the line of liquid. The stamp is then lowered intocontact with the substrate, displacing the liquid in front of it andproducing a thin, patterned layer of material under the stamp.

[0038] Another alternative involves application of the material to bepatterned as a droplet, either to the surface of the receiver substrateor to the raised-pattern surface of the stamp. The stamp is then broughtinto contact with the substrate surface, thereby molding the appliedmaterial in the pattern of the stamp. The material may be cured (e.g.,thermally) with the stamp in contact with the substrate. For example,this approach has been applied to liquid-phase polyimide, vinyl, andnanoparticle metal inks, which are cured by activating a hotplateunderlying the substrate following patterning. It is found, however,that this approach is most useful for insulators (such as polymers)because the resulting patterned film is contiguous. The process alsoworks best with viscous materials that exhibit limited outgassing duringcure (although PDMS stamps are to some degree porous to may outgassingcomponents).

[0039] FIGS. 3A-3C illustrate the embossing technique of the presentinvention as applied to a planar surface. A substrate 300 is coated witha thin, uniform film 305 of liquid as described above. An elastomericstamp 310 having a pattern of projecting and recessed features 315, 320is lowered until the projecting features 315 make contact with substrate300, thereby displacing liquid 305 at the regions of contact. The height(or heights) of the recessed features 320 exceeds that of the liquidthat will be displaced therein. The area dimensions of projectingfeatures 315 are constrained by the need for these features to pushaside the liquid 305 and either make contact with substrate 300 or atleast displace enough liquid to facilitate its convenient subsequentremoval. The maximum areas of features 315 depend greatly on theviscosity of the liquid, the thickness of the film 305, and the natureof the stamp elastomer. For metallic nanoparticles in suspension (15%)with a wet film thickness of 500 nm, it has been found that anelastomeric stamp formed from PDMS can completely transport thenanoparticle-containing liquid over a distance greater than 5 μm. Inorder to enhance the transport capability of features 315, these mayhave convex, rather than flat, surfaces; for example, the features maybe domed, peaked, or otherwise shaped to make contact with substrate 300at a small region, progressively moving more liquid as stamp 310 ispressed against substrate 300 and the features 315 flatten.

[0040] Stamp 310 is preferably lowered onto substrate 300 using a slightrocking motion. Since the stamp is elastomeric, it may be slightlyflexed so that one edge first makes contact with the substrate beforethe rest of the stamp rolls into place. This approach prevents orreduces the formation of air bubbles. No unusual pressure, temperature,or ambient conditions are necessary for the embossing process. Verylight or no pressure is applied to the stamp 310 so the projectingfeatures 315 penetrate the liquid film 305. Any attractive force betweenprojecting features 315 and substrate 300 will assist with the transportof liquid into recesses 320, and may also allow pressure to beremoved—so that features 315 merely rest against substrate 300—withoutsacrificing contact.

[0041] With the stamp 310 against substrate 300 as shown in FIG. 3B, thefilm 305 may be partially or completely cured. The curing mode isdictated by the nature of the liquid, and may include one or moreprocess steps such as heating, evaporating a solvent (to which theelastomer of stamp 310 is permeable), UV exposure, laser annealing, etc.Stamp 310 is removed from substrate 300 as shown in FIG. 3C, leaving apattern of fully or partially cured film traces 325 that correspond tothe pattern of recesses 320. Preferably, stamp 310 is removed using arocking motion. Smooth, uniform motion improves the quality of thepattern 325 and prevents damage thereto from minuscule bursts of air.

[0042] It is found that even if the liquid 305 is not cured while stamp310 is in contact with substrate 300, it will tend nonetheless to retainthe pattern 325 when stamp 310 is removed so long as the thickness ofthe liquid is sufficiently small. That is, there will be no detectableflow of liquid back into areas displaced by the projecting regions ofstamp 310, probably due both to the absolute height of liquid 305 andthe small contact angle between the liquid and substrate 300. Moreover,so long as the surface energies of the substrate 300 and the stamp 310are sufficiently mismatched, there will be no withdrawal of substratematerial by stamp 310. As a result, stamp 310 may be immediately reusedwithout cleaning.

[0043] If uncured or partially cured, the patterned liquid 325 may atthis point be cured into full solidity. In addition to the curingtechniques discussed above, the absence of the stamp 310 facilitatessuch additional mechanisms as vacuum evaporation and chemicalmodification (e.g., by addition of a cross-linker). In this regard, itshould be noted that the film patterned by the stamp 310 may begin as asolid rather than a liquid. For example, the film may be heated todecrease viscosity before stamp 310 is brought into contact therewith.Alternatively, stamp 310 may itself be heated to a temperaturesufficient to melt the solid film upon contact.

[0044] The film patterned by stamp 310 need not be planar; indeed, inconstructions involving multiple deposited and patterned layers,coplanarity among layers may frequently be disrupted to achieve desiredthree-dimensional configurations. FIG. 3D shows a substrate 300 having apreviously patterned layer of a first material 330. A thin film 335 ofliquid is drawn over material 330 and, where exposed, substrate 300; theliquid 335 is generally conformal, resulting in an uneven liquidsurface. Maintaining precise alignment among patterned layers isobviously vital to proper functioning of the finished device.

[0045] An elastomeric stamp 340 is well-suited to patterning such anuneven surface while maintaining precise rendition of the stamp pattern.As shown in FIG. 3E, stamp 340 is lowered as discussed previously.Because of its elastic character, stamp 340 deforms to allow differentprojecting features 345 to reach solid surfaces of different heightswithout substantial lateral deflection. As a result, the pattern 350 ofmaterial 335 that remains upon removal of stamp 340 is substantiallycomplementary to the pattern of projecting features 345, notwithstandingthe different heights of the embossed regions. Naturally, the degree offidelity to the stamp pattern depends on the degree of elasticityinherent in the stamp and the differences in height that must beaccommodated.

[0046] Following removal of stamp 340, the embossed pattern of material350 is cured. Of course, the curing mode chosen must not damage thepreviously cured layer 330.

[0047] As explained above, a thin film of deposited may be conformal,resulting in a surface of varying heights (rather than filling recessesto create a planar surface). The embossing technique of the presentinvention can be used not only to planarize such deposited layers, butalso to create “vias” that interconnect layers not directly in contactwith each other. With reference to FIG. 3G, a substrate 300 is patternedwith a previously deposited and embossed layer of a first material 360.A thin film 365 of liquid is drawn over material 360 and, where exposed,substrate 300; once again the liquid 365 is generally conformal,resulting in an uneven liquid surface. In many applications, it isdesirable for the component layer formed from liquid 365 to be planarrather than conformal. For example, planarization is essential formicroelectromechanical (MEM) structures and many-layer three-dimensionalcircuits. The present invention can accomplish both planarization andthe creation of vias among non-adjacent stratified layers.

[0048] As shown in FIG. 3G, the projecting features of a stamp 370(representatively indicated at 375) have elevations chosen such that,with the surfaces 377 of the projections in contact with substrate 373,the recessed portions of stamp 370 (representatively indicated at 380)make contact with the surface of liquid 365. As shown in FIG. 3H, theresult is planarization of the liquid layer 365 where it is in contactwith stamp surfaces 380. When stamp 370 is removed (FIG. 3I), that layeris substantially planar with the exception of edge ridges shown at 385.Moreover, a via 390 is established between the surface of substrate 300and the top surface of layer 365. A layer subsequently deposited onlayer 365, therefore, can make contact with substrate 300, and thissubsequently deposited layer can also be planarized in the manner justdescribed. Alternatively, the via 390 can be made to persist throughmultiple layers by embossing with a similar projecting feature as eachsuch layer is applied. In this way, contact between distant layers maybe effectuated.

[0049] If the elevation of projecting features 377 is insufficient,there will be no contact with substrate 300 and via 390 will not form.If the elevation of projecting features 377 is excessive, then liquid365 will not fully planarize; via 390 will effectively be stepped, withan intervening ridge or shoulder. Nonetheless, the latter sizing erroris preferable, since the via 390 will be functional and, moreover, theconfiguration shown in FIG. 3I can still be achieved by compression offeatures 375 (if substrate 300 can tolerate some applied pressure).

[0050] Liquid 365 may or may not be cured (totally or partially) beforestamp 370 is withdrawn in the manner hereinabove described. Followingcuring, the liquid 365 may decrease in height, jeopardizing planarity.This problem can be overcome by applying additional layers of the samematerial and embossing with the same pattern of features 377, 380. Theability to planarize and pattern in the same step represents asignificant fabrication capability and improvement over the prior art.

[0051] The foregoing approach, in which a stamp is made from a masterand then used repeatedly, may not be suitable for all applications. Analternative arrangement utilizes a device which, under computer control,is capable of changing its surface topology in accordance with a desiredpattern and then acting as a stamp. Such a device may be built, forexample, using an array of MEM elements that are actuatedelectrostatically, thermally, magnetically, piezoelectrically or byother computer-controllable means, actuation of an element causing it toalter the degree or manner in which it projects from the surface of thearray. One such device useful in the present application is amicro-mirror array in which an array of elements is caused to tilteither out of plane or lie flat depending on an electrical signal (seeKim et al., Society for Information Display 99 Digest, p. 982 (1999)).

[0052] The approach of the present invention can be used to createarbitrary functional devices. The technique is negative-working, in thesense that the pattern of projecting features corresponds to thematerial that will be removed rather than deposited. This designmethodology is apparent from FIGS. 4A-4F and 5A-5F, which illustratefabrication of a two-transistor electronic inverter. Each of FIGS. 4A-4Fis a section taken from the corresponding one of FIGS. 5A-5F along theline labeled with the figure number. Functional layers are built up on asubstrate 400 (FIGS. 4A, 5A), which may be, for example, a glass slide,a plastic sheet, a silicon wafer, or any other material having asufficiently smooth surface 400 s. Each added layer is patterned by adifferent stamp.

[0053] As shown in FIGS. 4B, 5B, a patterned conductive metal layer 410is established on surface 400 s of substrate 400. This is accomplishedby first applying a thin film of a metal-containing liquid, such as asuspension of gold or silver nanoparticles in a suitable carrier liquid(see, e.g., U.S. Pat. No. 5,756,197, the entire disclosure of which ishereby incorporated by reference). The applied liquid is patterned witha stamp as described above so as to create a series of channels thatreveal the surface 400 s of substrate 400. The liquid is then cured(e.g., in the case of a metal nanoparticle suspension, the carrier isevaporated so that the metal particles coalesce into a substantiallycontinuous, conductive patterned film). The pattern formed includes apair of transistor gaps 412, a ground rail 414, and a V_(cc) rail 416.

[0054] A semiconductive layer 420 is deposited onto the conductive layer410. Layer 420 completely fills and is planarized over the channels 412,so that in these locations, layer 420 is in contact with substrate 400.Otherwise, the pattern of layer 420 substantially matches that of layer410 so that the semiconductor 420 does not bridge between metal lines.In some areas 422, layer 420 is removed by the embossing process toreveal the underlying layer 410, while in other areas 424 overlyingchannels previously defined through layer 410, substrate 400 isrevealed. Semiconductive layer 420 may be applied as a liquid suspensionof semiconductor (e.g., silicon, germanium, CdSe, etc.) nanoparticles asdescribed, for example, in U.S. Pat. No. 5,534,056 (the entiredisclosure of which is hereby incorporated by reference). Again,following patterning, the layer may be cured by evaporating the carrierso as to coalesce the particles into a continuous patterned film.

[0055] An insulating layer 430 is applied over semiconductive layer 420as shown in FIGS. 4D, 5D. Layer 430 completely fills the vias 424, andis planarized thereover. A via 432, slightly smaller in diameter thanthe via 422 (see FIG. 4C) created earlier, is formed through that via422 to reveal layer 410. The insulating layer may be applied as anuncross-linked liquid polymer precursor, such as a radiation-curecoating (polyacrylates and polymethacrylates, for example, are suitablefor this purpose). Following patterning and removal of the stamp, thepolymer precursor may be cured (i.e., cross-linked) into solidity byexposure to UV or e-beam radiation.

[0056] With reference to FIGS. 4E, 5E, a second metal layer 435 isapplied to insulating layer 430 and patterned by stamping. A plug of themetal layer 435 completely fills the via 432 created previously andconnects to metal layer 410; because via 432 has a smaller diameter thanvia 424, a layer of insulating material separates the plug of metal fromsemiconductor layer 420 within the via 432. The second metal layer 430forms the gates 440 of the two transistors.

[0057] An encapsulant 450, such as a UV-cured polymer, epoxy or spin-onglass is applied as a coating over layer 435 to protect all underlyingfunctional layers from contamination or physical damage. Theencapsulant, which is applied at a sufficient thickness to fill allexposed channels, also adds structural rigidity to the finished device.

[0058] FIGS. 6A-6G and 7A-7G illustrate fabrication of a freely rotatingMEM wheel. Each of FIGS. 6A-6G is a section taken from the correspondingone of FIGS. 7A-7G along the line labeled with the figure number. Thestructure includes a first sacrificial or release layer, a secondsacrificial or release layer, a first metal layer, a third sacrificialor release layer, and a second metal layer. After all layers areapplied, a final release step etches away the release layers to liberatea purely metallic structure. Each layer is patterned using anelastomeric stamp as described above.

[0059] A substrate 600 (FIGS. 6A, 7A), which may be a glass slide, aplastic sheet, a silcion wafer, or any other appropriately smoothsurface (for MEM applications a relatively stiff substrate may bedesirable), receives a first release layer 610 as shown in FIGS. 6B, 6C.Release layer 610 may be, for example, a polymer (such as PMMA) solubleor wet-etchable in a solvent (such as acetone), or etchable by dry-etchtechniques (such as plasma etching); or may be a spin-on glass etchablein hydrofluoric acid. Release layer 610 completely covers substrate 600with the exception of a hole 612 patterned in the release layer by meansof the elastomeric stamp. This hole 612 will receive material for theaxle of the wheel.

[0060] The second release layer 620 is patterned as shown in FIGS. 6C,7C. The pattern includes a series of depressions 622. These will befilled with metal to create dimples on the rotating wheel. The hole 612is patterned in the center of layer 620.

[0061] With reference to FIGS. 6D, 7D, the first metal layer 630 fillsthe holes 612, 622 (see FIG. 6C) patterned in the first two releaselayers 610, 620. Layer 630 is planarized over these holes. Stampingeliminates metal from a pair of concentric circular regions 632, 635.Region 632 defines the edge of the wheel, and region 635 faciliatatesseparation of the wheel from the axle. The bottom of the wheel fills thedepressions 622 (FIGS. 6C, 7C), forming dimples that will reducestiction between the wheel and substrate 600. Not shown are small holespatterned in the wheel to allow etchant to reach the underlying releaselayers 610, 620.

[0062] The third release layer 640 is added and patterned as shown inFIGS. 6E, 7E. This layer uses a stamp identical to that employed topattern the first release layer 610, forming a hole 645 in the centerfor the axle of the wheel.

[0063] The second metal layer 650 (FIGS. 6F, 7F) is patterned to createa cap 652 on the axle of the wheel. This cap prevents the wheel fromleaving the axle after all release layers are etched away. Metal layer650 is also crosshatched to create small islands 655 of metal. Theseislands represent excess material and will be removed when the releaselayers are etched away, but are included to facilitate separation of therelease layers. During the release step it may be necessary to use asupercritical CO₂ release to avoid suckdown problems between the wheeland the substrate.

[0064] After the release layers 610, 620, 640 are etched away byexposure to a suitable solvent, the device assumes the configurationshown in FIGS. 6G, 7G. The finished device is a wheel 660 with dimples662 on its bottom surface, an axle 665 about which the wheel 660 is freeto rotate, and a cap 650 that holds the wheel 660 in place on the axle665.

[0065] Other MEM structures amenable to production using the presentinvention include, for example, so-called heatuators, linear combdrives, and combustion engines.

[0066] FIGS. 8A-8F illustrate use of the present invention to create aso-called “biochip,” i.e., an electronically active or readablesubstrate having a dense array of different biological materials (e.g.,DNA probes, protein probes, carbohydrates). Such a chip can be used, forexample, to identify samples of interest or to test for the presence ofvarious molecular sequences. See, e.g., U.S. Pat. Nos. 5,605,662,5,874,219, 5,744,305 and 5,837,832. If a sufficiently large array ofdifferent oligonucleotides can be deposited onto a surface, then one mayin principle obtain full genome sequence information via the method ofsequencing by hybridization (Skiena et al., Proc. 36th Ann. Symp. onFoundations of Comp. Sci., pp.613-20 (1995)). As shown in FIG. 8A, anelastomeric stamp 810 has a series of projecting features 815. Asubstrate 820 has deposited thereon a thin film of biological material822.

[0067] Stamp 810 is lowered until projecting features 815 penetrate anddisplace the liquid film 812 to make contact with the underlyingsubstrate 820 (FIG. 8B). The stamp 810 is then removed from contact withthe substrate 810, leaving a pattern 825 of biological material and acomplementary pattern of regions 827 from which biological material hasbeen removed (FIG. 8C).

[0068]FIG. 8D shows a second substrate 830 having an array of projectingfeatures 832 each with a biological receptor 835 bonded thereto. Thisbiological receptor uniquely bonds to constituents of the biologicalmaterial 822; for example, biological material 822 may be a proteinsolution, and the receptor 835 an antibody specific for the protein. Thesecond substrate 830 is aligned above the original substrate 820.

[0069] The second substrate 830 is brought into contact with substrate820 (FIG. 8E); some of the projecting features 832 overlie biologicalmaterial 825, while others overlie voids 827. Biological material bindsto receptors attached to projecting features that penetrate the liquid,while projecting features brought into contact with (or proximity to)void areas 827 remain unmodified. FIG. 8F shows the second substrate 830removed from contact with substrate 820. Biological material on theoriginal substrate was selectively transferred to certain projectingfeatures 832 of the second substrate 830 and not to others; the secondsubstrate 830, thus selectively patterned (with features 832 on theorder of 10 nm-100 μm) and chemically reacted, may serve as a biochip.The liquid material remaining on the original substrate 820 may be usedto produce additional biochips.

[0070] If desired, the biochip may be brought into contact with a thirdsubstrate having a different biological material, and which has beenpatterned with the original stamp 810 or with a different stamp. In thisway, a second layer of biological material can be selectively added tovarious of of the projecting features 832.

[0071] In an alternative approach, a biological resist layer ispatterned by an elastomeric stamp in accordance with the invention, andis then brought into contact with a substrate having projectingfeatures. The resist material binds selected projecting features basedon the respective patterns of the features and the resist. The entirestructure is then immersed in a functional biological material, whichbinds only to projecting features that have not received resist.Finally, the structure is immersed in an etch bath that removes theresist material (and any biological material that may have bound to it),but leaving undisturbed biological material bound to features that didnot receive resist.

[0072] In a second alternative, biological material may be directlytransferred from the projecting features of the elastomeric stamp ontoselected sites (e.g., raised features) on the substrate. Areas of thestamp corresponding to recessed features do not transfer material. Inthis fashion the substrate may be patterned without the need for anintermediate transfer step. Spreading of the transferred material isavoided by maintaining only a very thin film of material in the platefrom which the stamp is “inked.” It is important, of course, that thereceiver surface exhibit a higher affinity for the biological materialthan the stamp. PDMS has a very low surface energy, making it ideal fortransferring a wide range of materials.

[0073] It should be stressed that this “direct pattern transfer”approach to patterning can be employed in connection with materialsother than biological liquids. For example, a metal nanoparticledispersion may be applied as a thin film to a flat surface such as glassor plastic. A patterned elastomeric stamp is brought into contact withthe film of material and withdrawn, and the material adhering to thestamp transferred to a second surface. Using this technique, we haveobtained conducting structures with edge resolutions on the order of 300nm.

[0074] Existing methods for making DNA chips, such as described in U.S.Pat. No. 5,744,305, are limited in resolution and in requiring DNAarrays to be constrained to planar and non-porous surfaces. Using thestamping methods of the present invention and standard nucleotidechemistry (such as that used in gene-assembly machines), a DNA biochipmay be fabricated in which nucleotides are added one base unit at a timeto build up an array of spatially separated oligonucleotides that differin their sequences as a function of location. For example, chemicalsynthesis of DNA can be accomplished by sequential addition of reactivenucleotide derivatives. Each new nucleotide in the sequence is firstblocked by reaction with 4′,4′dimethoxytrityl (DMT) and then combinedwith a highly reactive methylated diisopropyl phosphoramidite group,which links the nucleotide with the one previously added. The blockinggroup is removed by detritylation, which renders the newly linkednucleotide available for linkage to a further nucleotide. When synthesisis complete, all methyl groups are removed by exposure to alkaline pH.

[0075] Similarly, by employing the standard chemistries used inprotein-assembly machines (e.g., repeated sequences of chemicallyblocking an amino acid, activation, linkage to the most recently addedamino acid, followed by unblocking), carbohydrate-assembly machines,protein or carbohydrate biochips may be fabricated. In such biochips itmay be desirable to have good separation between biological domains(such as between oligonucleotides of different sequence). This may beaccomplished by stamping such sequences onto a non-planar or poroussurface. In this context, the term “porous” refers to non-planarfeatures that physically separate unique nucleotide sequences (or otherchemically distinct biomolecules). For example, each sequence may bepatterned on the top surface of a raised pillar, each of which isphysically separated from its neighbors. This design allows forconvenient removal unwanted chemistries, since these can be continuouslywithdrawn as they accumulate at the bases of the pillars. Alternatively,each nucleotide sequence may be deposited into a separate recessed well.

[0076] The stamping process of the present invention can be efficientlydeployed to produce repetitive circuit patterns in two or threedimensions using a single set of stamps. FIG. 9A schematicallyillustrates a single SRAM 900 circuit with a power rail V_(cc) 910 and aground rail 915. The SRAM 900 is addressed using a horizontal controlline 920 and a vertical control line 925 which, when both high, activatethe split-gate transistor structure 930 and connect the read/write line935 to the memory cell. The volatile memory is stored in a pair ofcross-coupled inverters 940. This circuit can be fabricated using theembossing technique with five different elastomeric stamps: two metallayers, a semiconducting layer, a thin insulating layer, and aplanarizing layer with vias.

[0077]FIG. 9B shows the manner in which the basic circuit 900 can beutilized as a “tile” in a two-dimensional array of such circuits. In thefigure, the circuit 900 is replicated 16 times in a contiguous, 4×4two-dimensional array 950. This memory array 950 has power and groundrails, the horizontal control lines running along the left and rightedges 955, and the vertical control lines and read/write lines runningalong the top and bottom edges. The array 950 is produced by applying,in the pattern of the array, the same five stamps over each appliedlayer. The stamped regions interact to form the continuous circuit 950.

[0078] As shown in FIG. 9C, the array can be extended into threedimensions by replicating the two-dimensional array 950 in a verticalstack 970. A memory address is divided so that the first bits of theaddress decode into a set of horizontal control lines that all lie inthe same two-dimensional position but are stacked vertically, and thelast bits of the address decode the vertical control lines in the sameway. In this fashion a word of memory is stored in the sametwo-dimensional position of different arrays in the vertical stack (sothat the number of bits in a word of data corresponds to the number ofvertically stacked memory arrays). The decoding circuitry on the edgesof the memory may also be produced using the same five masks repeatedfor each layer with vias interconnecting the layers.

[0079] This approach is well-suited to construction of so-called“cellular automata,” which are interconnected processing cells thatinteract with neighbors to compute in parallel. Cellular automata areoften used to simulate three-dimensional environments, but conventionalapproaches are inherently two-dimensional and therefore limited inprocessing capacity. By creating circuits in three dimensions with manylayers, it is possible to overcome this scaling limitation. Acellular-automata device would include many two-dimensional arrays ofcells stacked vertically to create an interconnected three-dimensionalarray.

[0080] Another example of three-dimensional devices amenable tofabrication in accordance with the present invention is a neuronalstructure consisting of many individual electronic “neurons” (eachrepresented by a processor) arranged in three-dimensions with many“dendritic” interconnects between neighboring devices. Each neuron isaffected by all of its surrounding neurons and in turns affects theneurons to which it is connected. Neural networks created inthree-dimensions avoid many of the scaling problems that plague today'stwo-dimensional circuits.

[0081] Another application of the stamping process of the presentinvention involves creation of electron-emission structures for use infield-emission displays (FEDs). Today, these devices are typicallyfabricated in silicon and are quite expensive and complicated toproduce; the most common structure used is a Spindt-tip. Recently,research has shown that by using materials with a lower work function(e.g., single-wall carbon nanotubes), much simpler structures can befabricated with equal or better efficiency than typical silicon emitters(Choi et.al., Society for Information Display 99 Digest, p. 1134(1999)). Unfortunately, the growth temperatures for producing nanotubesare well above the melting point for glass or plastic substractes(exceeding 800° C.) and have thus not been integrated with processesemploying such substrates.

[0082] In accordance with the present application, a slurry of metallic(preferably gold) nanoparticles and chopped up nanotubes (nanopipes) isdissolved in a solvent. As shown in FIG. 10A, this slurry is thenpatterned, by stamping, onto a substrate 1010 (e.g., a glass sheet) assets 1020, 1025 of interdigitated lines; some carbon nanotubes 1030 willprotrude from the surfaces of the lines 1020, 1025. Through any ofvarious available techniques (e.g., application of an electric field, orexploiting the flow of the liquid as the stamp is released), thesenanotubes may be positioned to all point in the same directions. Lines1020, 1025 are then cured at temperatures below 300° C.

[0083] With reference to FIG. 10B, another layer 1040 of thenanoparticle slurry is applied so as to completely cover one set oflines 1020, thereby fully enclosing the carbon nanotubes. This set oflines 1020 represents the gate of the FED, whereas the set of lines 1025represents the cathode. In operation, a phosphored anode 1050 isdisposed proximately and in opposition to lines 1020, 1025, and a highvacuum established between anode 1050 and substrate 1010. Two parametersgovern the operation of the FED: the voltage between the anode 1050 andthe cathode lines 1025 (V_(ac)), and the voltage between the gate lines1020 and the cathode lines 1025 (V_(gc)). The FED is either on or off.To set the FED to the “on” state, V_(ac) is set to about 20V and V_(gc)is set to 0V; electrons will stream from the cathode lines 1025 to theanode 1050 due to the low work function of the carbon nanotubes, butelectrons will not stream from the gate lines 1020 to the anode 1050. Toset the FED to the “off” state, V_(ac) remains at about 20V but V_(gc)is set to 5V; the electrons from cathode lines 1025 will then stream tothe gate lines 1020 and no electrons will stream to the anode 1050. Avisual display is caused by selective, line-by-line activation of thecathode lines 1025 to cause electron streaming therefrom.

[0084] In another application, the stamping process of the presentinvention may be combined with existing chip-fabrication processes. Forexample, the current high-end microprocessor production process can bedivided into two major steps: the “front-end” processing, which consistsof all steps necessary to produce a working transistor (e.g., silicongrowth, gate oxide, doping, transistor fabrication); and the “back-end”processing of the wafer that creates the metal interconnects and viaswhich establish connections among the transistors. For high-end chipsthere may be a total of 30 mask sets, 18 for front-end processing and 12for back-end processing; the complexity and cost of a chip is generallydetermined by the number of mask sets employed in its fabrication.

[0085] In accordance with the present invention, stamping is used toproduce the metal back end for an otherwise typically fabricatedsilicon-wafer front end. A wafer is produced using standard siliconfront-end processes up until the point when metal would first bedeposited. Then, instead of evaporating aluminum and applying it usingplasma etching, CPVD, CMP, Damascene planarization, and/or the othertraditional processes (which tend to be expensive, lengthy, difficult,and wasteful), layers of metallic nanoparticles are patterned bynanoscale embossing to form the interconnect layers; in particular, athin film of a metal nanoparticle solution is applied (e.g., by aspin-on technique) onto the wafer, and the film is patterned byembossing as described above to form metal interconnects and to fill thevias to underlying layers. The conducting traces thus formed are cured,and a layer of a dielectric nanoparticle material is deposited thereon.This layer is then embossed to pattern vias between metal layers, andthen cured. The steps of depositing, patterning, and curing conductiveand insulating layers are repeated until the desired number of layers isattained.

[0086] This approach offers advantages in terms of cost, time, waste,and difficulty of production; but, in addition, it also has theadvantage of being self-planarizing. As a result, each layer ofdialectric can be planarized through the stamping process, so that it ispossible to create many more layers than can be obtained using current,conventional processes. In addition, since the stamping process isconformal to underlying layers, the quality of the planarization is notcritical (as is the case, for example, in photolithography, where eachlayer must be planar to within a few hunder nanometers).

[0087] Still another application the stamping process of the presentinvention is fabrication of organic light emitters, organic logic, andorganic transistors. Organic light emitters and logic materials such asPPV (poly(p-phenylene vinylene) and thiophene are difficult to patternusing standard lithographic processes because the etch process candegrade the organic material. One alternative approach is to use ink jet(Shimoda et al., Society for Information Display 99 Digest, p. 376(1999)), but the resolution of this process is limited to above 10 μm.The stamping process described herein facilitates patterning ofsignificantly finer features.

[0088] Yet another application of the stamping process of the presentinvention is patterning of optical waveguides. An optical waveguide is astructure in which a first region possesses a first index of refractionand a second region possesses a second index of refraction. A verysimple optical waveguide may be made by simply embossing a rectangularridge in an optically transparent material (such as spin-on glass or UVoptical polymer) surrounded by air. Light directed into one end of theridge will emerge at the other end. By combining such printed opticalwaveguides with printed light emitters such as organicelectroluminescent materials, inorganic electroluminescent materials orhybrid electroluminescent materials and with printed detectors (such asphototransistors or photodiodes) and switches (such as electro-opticalswitches), it is possible to construct an “all-printed” or partiallyprinted switching fabric for control of incoming optical signals andtransmission of output optical signals for variousoptical-telecommunications applications.

[0089]FIG. 11 shows a block diagram of a preferred nano-embossingsystem, indicated generally at 1100. The system operates on a substrate1110, which is secured to a Z-translation stage 1115. The Z-translationstage is secured to a 360° theta stage 1120, which rotates in the XYplane. Theta stage 1120 is itself secured to a carrier 1125 on a gantrysystem 1130 adapted for two-dimensional movement in the XY plane. Thesecomponents can transport substrate 1110 to any spatial position withinthe limit of movement, and with arbitrary XY rotation. A series offunctional modules are suspended above substrate 1120, each moduleperforming a different step in the embossing process: depositing thinfilms of material on the substrate, patterning the thin film, and curingthe film following embossing.

[0090] In particular, thin films of liquid are produced on substrate1110 by a metal rod 1135 ₁ and an ejection device 1140 ₁ (e.g., an inkjet head or pipet) that deposits a small amount of liquid as describedabove in connection with FIGS. 2A, 2B. Additional sets of metal rods andejection devices (representatively indicated at 1135 ₂, 1140 ₂) areavailable for deposition of different liquids. The deposited liquidfilms are patterned by an elastomeric stamp, which may be selected froma plurality of available stamps representatively shown at 1150 ₁, 1150₂. The stamps are each retained within a suitable stamping press (notshown), the outer contours of the stamps fitting within complementaryrecess within the stamping equipment.

[0091] The patterned films are cured by a device 1160 (e.g., a thermallamp, a UV lamp, a laser, etc.) as appropriate to the film. Thesubstrate 1110 travels back and forth between these different modulesand an aribtrary number of layers may be patterned thereon. Alignment ofthese different modules with respect to substrate 1110 can beaccomplished, for example, using optical fiduciary marks as commonlyused for silicon mask alignment. In addition, fine-grained alignment ofthe stamps 1150 may be performed using physical self-alignment of thestamp. For example, each stamp 1150 may contain deeply recessedtriangular features that merge with raised alignment features on thesubstrate 1110. The stamp itself is preferably capable of translationand rotation during alignment.

[0092] Alternatively, a nano-embossing system in accordance with thepresent invention may comprise a “roll-to-roll” process facilitatingcontinuous production of functional devices. A roll-to-roll processresembles conventional letterpress printing processes, with the stampsof the present invention configured as elastomeric letterpress plates. Aplate is rotated on a drum, making gentle contact with a movingsubstrate onto which the curable liquid has been deposited.

[0093] Nanoparticles in solution for use with the present invention maybe fabricated using a process similar to chemical vapor deposition(CVD), alternative configurations for which are illustrated in FIGS. 12Aand 12B. With reference to FIG. 12A, controlled flows of a CVD precursorgas and an inert carrier gas are introduced into a heated vacuum chamber1200 through respective mass-flow controllers 1210, 1215. The chamber1200 is generally tubular in shape and is heated by a surroundingresistive coil. The wall of chamber 1200 is substantially transparent toradiation from a pair of orthogonally oriented lasers 1225 ₁, 1225 ₂.The organic capping material is introduced in vapor form into chamber1200, downstream of lasers 1225 ₁, 1225 ₂, by means of a flow controller1230. A collecting table 1232 is disposed within chamber 1200 stillfurther downstream, and is chilled by recirculation of a cooling fluidthrough a pair of valves 1235 ₁, 1235 ₂. Gaseous material is drawnthrough chamber 1200 in the direction of the arrow by a vacuum source(not shown).

[0094] As the CVD precursor travels through chamber 1200, it isdissociated by a combination of the elevated temperature in the chamberand energy imparted by lasers 1225 ₁, 1225 ₂. The respectiveconcentrations of CVD precursor and inert carrier are chosen such thatmean free path of the chemically pure, dissociated elements or moleculespermits, on a probabilistic basis, only hundreds of collisions withother like species before the organic vapor introduced through flowcontroller 1230 is encountered. With each collision, more and more ofthe dissociated species come together, thereby forming larger particles.Capping this growing particle with an organic shell prevents it fromfurther increasing in size. The inert gas carries the growing particlesfrom the dissociation region to the capping region at a known rate, andonce capped, the particles are collected on chilled collecting table1232. The carrier gas and unreacted precursor exit the chamber 1200. Theresulting nanoparticles 1240, in the form of a paste on the plate 1232,are then removed from the vacuum chamber and put into solution. Thesolution is subjected to gravity or centrifuging, and the nanoparticlesof the smallest size are skimmed off the top.

[0095] Suitable CVD precursors include silane, TIBA (tri-isobutyl-Al),WF₆, and Cu(hfac)₂ (i.e., copper hexafluoroacetylacetonate) with heliumand argon as inert carrier gasses. Suitable organic capping groupsinclude straight-chain alkyl groups that chemically bond to theparticle, or groups that interact with the particle surface through aheteroatom such as sulfur, oxygen, nitrogen, or silicon. Other suitableorganics, as disclosed in U.S. Pat. No. 5,750,194, includealpha-terpineol, methyl oleate, butyl acetate, glyceride linoleate,glyceride linolenate, glyceride oleate, citronellol, geraniol, phenethylalcohol, and nerol.

[0096] As shown in FIG. 12B, the use of more reactive species justifiesa simpler configuration that may include a vacuum chamber 1250, which isevacuated by a vacuum pump 1260 operating through a valve 1260. A CVDprecursor gas and an organic capping group in vapor form are introducedinto vacuum chamber 1250 through respective mass-flow controllers 1260,1265. The CVD precursor quickly agglomerates into particles, and iscapped by the organic vapor. The particles 1270 collect on a chilledtable 1275, and are collected as described above.

[0097] Although the present invention has been described with referenceto specific details, it is not intended that such details should beregarded as limitations upon the scope of the invention, except as andto the extent that they are included in the accompanying claims.

What is claimed is:
 1. A method of fabricating a functional component,the method comprising the steps of: a. providing a thin film of acurable material in liquid form; b. patterning the curable material byembossing the material at low pressure with an elastomeric stamp havinga raised pattern thereon; c. curing the patterned material; and d.repeating steps (a) to (c) a plurality of times with materials which,when cured, have varying functional characteristics, the cured layersinteracting so as to produce a functional component.
 2. The method ofclaim 1 wherein the stamp comprises an elastomeric polymeric matrix witha rigidity-conferring material entrained therein.
 3. The method of claim1 further comprising the step of forming the elastomeric stamp by: a.creating a negative impression of the pattern in a substrate; b.enclosing the pattern; c. pouring a liquid elastomeric precursor intothe enclosure, the precursor flowing into the negative impression of thepattern d. curing the elastomeric precursor into an elastomer; and e.removing the elastomer from the substrate.
 4. The method of claim 1further comprising the step of forming the elastomeric stamp by: a.providing a photosensitive elastomer; b. exposing the elastomer toactinic radiation so as to render the pattern; and c. photochemicallydeveloping the exposed elastomer to produce the pattern.
 5. The methodof claim 1 further comprising the step of cleaning the stamp by applyinga liquid polyimide thereto, curing the polyimide, and removing the curedpolyimide from the stamp.
 6. The method of claim 1 wherein the curablematerial is applied as a liquid.
 7. The method of claim 6 wherein theliquid is applied onto a smooth, flat support as a bead and drawn into auniform film.
 8. The method of claim 1 wherein the curable material isapplied as a non-liquid and subsequently liquefied.
 9. The method ofclaim 8 wherein the material is applied to a support and liquefied byheating the support.
 10. The method of claim 8 wherein the material isliquefied by heating the stamp.
 11. The method of claim 1 wherein theraised pattern comprises convex surfaces.
 12. The method of claim 1wherein the stamp is applied to the patterned material and removedtherefrom with a rocking motion.
 13. The method of claim 1 wherein thematerial is present on a support and is at least partially cured withthe stamp held against the support.
 14. The method of claim 1 whereinthe stamp is removed from the material prior to curing the material, thematerial retaining the pattern despite removal of the stamp.
 15. Themethod of claim 1 wherein the material is present on an uneven surface,the stamp patterning the material without substantial lateraldeflection.
 16. The method of claim 1 wherein the material is present onan uneven surface, the stamp having unraised portions which, with theraised features in contact with the surface, planarize the material incontact with the unraised portions.
 17. The method of claim 1 wherein aplurality of contiguous layers is patterned with elastomeric stamps atleast some of which have different patterns, at least some of the stampshaving raised features in common locations to create vias betweennon-adjacent layers.
 18. The method of claim 17 wherein at least some ofthe vias extend through a plurality of layers.
 19. The method of claim17 wherein the vias are filled by deposited material forming one of thelayers, said material being planarized as said layer is patterned. 20.The method of claim 1 wherein the material of at least one of the layersis a suspension of nanoparticles in a carrier liquid.
 21. The method ofclaim 20 wherein the material is cured by evaporating the carrierliquid, the nanoparticles coalescing into a substantially continuouspatterned film.
 22. The method of claim 21 wherein the nanoparticles aremetal, the film being conductive.
 23. The method of claim 21 wherein thenanoparticles are semiconductive, the film being semiconductive.
 24. Themethod of claim 1 wherein at least one of the layers is soluble in asolvent, and further comprising the step of removing the at least onelayer by exposure of the component to the solvent.
 25. The method ofclaim 1 wherein, for each layer, the stamp is applied at a plurality oflocations to produce a two-dimensional repetitive pattern.
 26. Themethod of claim 1 wherein steps (a) to (d) are repeated a plurality oftimes so that the cured layers are formed repetitively.
 27. The methodof claim 1 wherein application of the stamp to the thin film results inadherence of material to the raised stamp pattern, the embossing stepcomprising transferring the adhered material to a substrate for curing.28. The method of claim 27 wherein transfer is accomplished byapplication of low pressure to the stamp.
 29. The method of claim 1wherein the thin film is formed by deposition of the curable material indroplet form followed by application of the stamp thereto so as to forma thin film having a pattern complementary to the stamp pattern.
 30. Themethod of claim 1 wherein the functional component is a micromechanicalstructure.
 31. The method of claim 1 wherein the functional component isan integrated circuit, the cured layers comprising conducting,dielectric, and semiconducting layers.
 32. The method of claim 1 whereinthe functional component is a biochip.
 33. The method of claim 1 whereinthe functional component is a field-emission display.
 34. The method ofclaim 33 wherein the curable material is a suspension of metalnanoparticles and carbon nanotubes and the pattern comprises first andsecond sets of interdigitated lines having nanotubes protrudingtherefrom, the repeating step comprising applying a suspension of metalnanoparticles so as to cover the first set of interdigitated lines andcuring the metal-nanoparticle suspension thereover.
 35. The method ofclaim 1 wherein the functional component is an optical waveguide.
 36. Anintegrated circuit fabricated in accordance with claim
 31. 37. A biochipfabricated in accordance with claim
 32. 38. A field-emission displayfabricated in accordance with claim
 38. 39. An optical waveguidefabricated in accordance with claim
 35. 40. A method of fabricating afunctional component, the method comprising the steps of: a. providing athin film of a liquid on a support; b. patterning the liquid byembossing it at low pressure with an elastomeric stamp having a firstraised pattern thereon, the raised pattern displacing the liquid whenbrought into contact with the support; and c. bringing into contact withthe support a substrate having thereon a second raised pattern, theliquid, where present on the support, adhering to the second raisedpattern.
 41. The method of claim 40 wherein the liquid comprises abiological material.
 42. The method of claim 40 wherein the liquidcomprises a biological resist, and further comprising the step ofexposing the substrate to a biological material, the biological materialnot adhering to raised portions of the substrate that have received theresist.
 43. A method of fabricating a functional component, the methodcomprising the steps of: a. providing a thin film of a liquid on asupport; b. patterning the liquid by embossing it at low pressure withan elastomeric stamp having a raised pattern thereon, the raised patternhaving at least some features with submicron dimensions and displacingthe liquid when brought into contact with the support; and c. curing thepatterned material.
 44. Apparatus for fabricating a functionalcomponent, the apparatus comprising: a. means for applying a thin filmof a curable material in liquid form; b. an elastomeric stamp having araised pattern thereon, the raised pattern having at least some featureswith submicron dimensions; c. means for applying the elastomeric stampto the curable material so that the raised pattern displaces thematerial; and d. means for curing the patterned material.